Why is there such a ridiculous ammount of Touhou art on this platform compared to anything else?

Apology if this isn't the right place to ask.

Do you want the long answer or the short answer?

It's not the right place to ask.

But the answer is quite simple, it has one of the longest running and most dedicated fan art and doujinshi community. There's more content, of a high quality, to upload compared to any other IP. Even Blue Archive and FGO kneel before them.